Deep frying

thumb|right|alt=Two parcels of pastry being lowered in a basket into oil|A chef deep frying [[fish and chips]]

Deep frying (sometimes referred to as deep fat frying) is a cooking method in which food is submerged in hot fat, traditionally lard but today most commonly oil, as opposed to the shallow frying used in conventional frying done in a frying pan. Normally, a deep fryer or chip pan is used for this; industrially, a pressure fryer or vacuum fryer may be used. Deep frying may also be performed using oil that is heated in a pot.<!--

Deep-fried dough was eaten as early as the late 2nd millennium BC in Canaan. Frying food in olive oil is attested in Classical Greece from about the 5th century BC. The 5th century AD Roman cookbook Apicius (De Re Coquinaria) offers a recipe for deep fried chicken in a cream sauce "Pullus leucozomus" fried in olive oil. Sanskrit texts such as the 12th century Manasollasa (Bhartur Upabhogakāraṇa) mention snacks like malpua and vataka being submersed and fried in ghee. Deep-fried foods such as funnel cakes arrived in northern Europe by the 13th century, and deep-fried fish recipes have been found in cookbooks in Spain and Portugal at around the same time.

French fries, invented in the early 17th century in Chile, became popular in the early 19th century western Europe. In 1860, Joseph Malin combined deep fried fish with chips (french fries) to open the first fish and chip shop in London.

Modern deep frying in the United States began in the 19th century with the growing popularity of cast iron, particularly around the American South which led to the development of many modern deep-fried dishes. with foods such as onion rings, deep-fried turkey, and corn dogs all being invented in the early 20th century. In recent years, the growth of fast food has expanded the reach of deep-fried foods, especially french fries.

Technique

thumb|225px|alt=Rings of dough in oil, varying in colour from light to dark|[[Smultring being deep-fried]]

Deep frying food is defined as a process where food is submerged in hot oil at temperatures typically between and , but deep frying oil can reach temperatures of over 400 °F (205 °C). One common method for preparing food for deep frying involves adding multiple layers of batter around the food, such as cornmeal, flour, or tempura; breadcrumbs may also be used.

When performed properly, deep frying does not make food excessively greasy, because the moisture in the food repels the oil. The hot oil heats the water within the food, steaming it; oil cannot go against the direction of this powerful flow because (due to its high temperature) the water vapor pushes the bubbles toward the surface. As long as the oil is hot enough and the food is not immersed in the oil for too long, oil penetration will be confined to the outer surface. Foods deep-fried at proper temperatures typically absorb less than per of oil used. This oil absorption rate is around the same as occurs with shallow frying, An informal test for a temperature close to this range involves adding a tiny amount of flour into the oil and watching to see if it sizzles without immediately burning.

Japanese deep frying tools include long metal chopsticks; the agemono-nabe deep frying pot, which is heavy for retaining heat and deep for holding oil; the ami-shakushi net ladle used for scooping out batter debris; and the abura-kiri oil drying rack pan. There are hundreds of dishes that are associated with deep frying as most foods can be deep-fried. Examples of food that can be deep-fried include meat, poultry, fish and vegetables. Fish and chips, for instance, combines deep-fried fish and deep-fried potatoes. French fries, doughnuts, onion rings, and hushpuppies are common deep-fried foods. Other common deep-fried foods include Chinese you bing deep-fried pancakes, Southeast Asian jin deui, and Japanese tempura. Less common deep-fried foods include maple leaves, pizza, Mars and Snickers bars.

In the United States, the Chicago Tribune notes that "you can deep fry almost anything". The American South has been noted as a modern center of innovation in the area of deep-fried food. According to the owner of a deep frying restaurant in the South, "If something is edible, you can bet that someone south of the Mason-Dixon line has tried to cook it in oil". A common food in this region is the deep-fried fritter, also referred to as "sponges". Deep-fried foods in the country of South Africa include fish and chips, vetkoek and koeksisters, among others.

Asia

thumb|225px|Deep-fried insects for human consumption sold at food stall in [[Bangkok, Thailand|alt=Large baskets of insects and scorpions at a market.]]

Japanese tempura is a popular deep-fried food that generally consists of battered and fried seafood and vegetables. Japanese deep-fried dishes, or Agemono, include other styles besides tempura, such as Karaage, Korokke, Kushikatsu, and Tonkatsu.

In areas of Southeast Asia such as Thailand, insects are commonly deep-fried for human consumption. Western-style fast food items such as donuts, deep-fried chicken, and deep-fried potatoes are also becoming popular in Asia.

In Indonesia deep fried food is quite common, serving as either a main dish or a snack. The ingredients are usually deep fried in palm oil, the most widely used cooking oil in the country. Some popular deep fried foods include ayam goreng (chicken), pecel lele (catfish), pempek (fishcake) and tempeh. Fritters in Indonesia is generally identified as gorengan, the most popular one including pisang goreng (banana fritter), bakwan jagung (corn) and tahu goreng (tofu).

Deep-fried fish, tofu, and ' are commonly eaten in Vietnamese cuisine. Deep frying is also used to make several kinds of ', including ' (fried rice ball), ' (sesame ball), ' (hollow doughnut), ' (sweet potato pancake), ' (banana fritter), Hồ Tây–style ' (shrimp fritter), and ' (pillow cake).

Deep-fried sticks of dough, known as youtiao in Chinese, are eaten in many East and Southeast Asian cuisines.

In Hong Kong, deep-fried intestine of pigs is a popular food.

In South Asia, popular deep fried snacks are samosa, jalebi, and pakora.

Europe

Many countries such as the United Kingdom use pure or hydrogenated rapeseed oil for deep-frying. Fish and chips is a very popular deep-fried dish in the U.K. since it originated in London in the 19th century and became popular among the working class. Its popularity continues with 229 million portions of fish and chips being sold annually in England alone.

There is an annual trade fair devoted to deep-fried foods called the International Symposium on Deep-Fat Frying which features discussions on deep fat frying as well as exhibitions by companies involved with the process.

Belgian tradition requires French fries to be deep-fried in filtered fat of cattle, locally called blanc de boeuf or ossewit.

The Mediterranean diets traditionally use olive oil for deep-frying, which it is absorbed by the food in the process. Research indicates that virgin olive oil is unique among other cooking oils because it is very rich in monounsaturated fatty acids and contains beneficial micronutrients.

The deep-fried Mars bar originated in Scotland, with The Carron Fish Bar in Stonehaven claiming to have invented it in the early 1990s.

North America

In the United States, soybean oil is often used for deep-frying. Hundreds of items are served at these fairs. Some of them include deep-fried beer, butter, and bubblegum. Additionally, deep frying can be used as a form of artwork by frying non-edible objects, such as electronics. Artists such as Henry Hargreaves have deep-fried replicas of electronic items such as iPads, Game Boys, and laptops.

Deep-fried food contests are frequently held at fairs such as the Texas State Fair, where they hold an annual contest for the most creative deep-fried food. Notable past winners have included fried Coke and deep-fried butter, both invented by Abel Gonzales. Since 2013, an American reality competition show called deep-fried Masters, produced by Discovery Networks, holds deep frying competitions at several state fairs across the country.

Oceania

Fish and chip shops in Australia may purvey several types of deep-fried foods, along with other food types.

South America

thumb|225px|[[Buñuelos|alt=Fried balls of dough in a basket.]]

The buñuelo, a fried dough ball popular in Central America and Greece, is a popular deep-fried snack and street food in South America.

Overheating or over-using the frying oil leads to formation of rancid-tasting products of oxidation, polymerization, and other deleterious, unintended or even toxic compounds such as acrylamide (from starchy foods). Recent research suggests fat deterioration may be worse when fat or oil is fried with food than when fat or oil is tested on its own in a laboratory. Deep-frying under vacuum helps to significantly reduce acrylamide formation, but this process is not widely used in the food industry due to the high investment cost involved.

Some useful tests and indicators of excessive oil deterioration are the following:

Sensory – darkening, smoke, foaming, thickening, rancid taste and unpleasant smell when heating. This is the most unreliable way to decide when to change oil because those are very individual factors and can depend on different causes.
Testing strips – decide when to change oil depending on FFA (free fatty acids) only
Oil-tester – measurement tool to exactly define the point of change oil by TPM/TPC (Total polar material/compounds)
Laboratory – acidity, anisidine value, viscosity, total polar compounds, polymeric triglycerides.

Instruments that indicate total polar compounds, currently the best single gauge of how deep-fried an object is, are available with sufficient accuracy for restaurant and industry use.

Hazards

thumb|left|200px|When deep frying, fires can be very severe, with chip pan fires being the leading cause of house fires in the United Kingdom.|alt=A pillar of fire erupts from a pan and spreads across the ceiling above.

Cooking oil is not flammable at room temperature but can become flammable when used at high temperatures. Further, attempts to extinguish an oil fire with water can cause an extremely dangerous condition (a slopover) or firefighting foam. Most commercial deep fryers are equipped with automatic fire suppression systems using foam.

Spilled hot cooking oil can also cause severe third degree burns; in the worst-case scenario, severe burns can be fatal. The higher temperatures If children are present, the utmost care should be used when deep frying so that their safety can be protected at all times.

Environmental

thumb|right|225px|A bin for spent cooking oil in [[Austin, Texas, managed by a recycling company|alt=A large bin, with "GREASE ONLY" stamped on the lid.]]

Deep frying produces large amounts of waste oil, which must be disposed of properly. Waste oil can contribute to the creation of fatbergs, overflow sewage systems, bind to the walls of sewage pipes, and interfere with sewage treatment. Waste oil from deep frying is increasingly being recycled and refined into biodiesel. Potatoes that are stored in artificially humidified warehouses contain more water, which makes the time required to deep fry them into chips longer. This increases the carbon dioxide footprint of commercially producing chips because more energy is required for frying over a longer time.

Health

The process of deep frying food is generally detrimental to its nutritional value. The oils that foods absorb in their batter typically contain large amounts of saturated fats and trans fats. Consumption of large amounts of saturated and trans fats has been linked to a higher risk for some cancers.

Eating deep-fried foods has also been linked to higher cholesterol levels, obesity, heart attacks, and diabetes. Deep-fried foods cooked at certain temperatures can also contain acrylamide. This discovery in 2002 led to international health concerns. Subsequent research has however found that it is not likely that the acrylamides in burnt or well-cooked food cause cancer in humans; Cancer Research UK categorizes the idea that burnt food causes cancer as a "myth".

Additionally, fat degradation processes (lipid peroxidation) during deep frying results in the loss of nutritional value in deep-fried foods.

Cooking oil that has been used for too long may in addition cause blood pressure elevation and vascular hypertrophy.

Trans fats are used in shortenings for deep-frying in restaurants, as they can be used for longer than most conventional oils before becoming rancid. In the early 21st century, non-hydrogenated vegetable oils that have lifespans exceeding that of the frying shortenings became available. As fast-food chains routinely use different fats in different locations, trans fat levels in fast food can have large variations. The amount of trans fat that is formed during frying appears to increase with frying temperature, frying time, oil oxidation, and oil reuse.

Some studies have found that deep frying in olive and sunflower oils has been found to be less of a detriment to health and in some cases have positive effects on insulin levels.

Technique

Asia

Europe

North America

Oceania

South America

Hazards

Environmental

Health

See also

References

Further reading

External links